Imaging of metastatic or recurrent cancer

ABSTRACT

The present disclosure relates to methods of administering [18F]-FACBC. The present disclosure also relates to use of [18F]-FACBC in methods for imaging, diagnosing and monitoring metastasis or recurrence of cancer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/160,227 filed on Oct. 15, 2018, now U.S. Pat. No. 10,716,868, whichis a continuation of U.S. application Ser. No. 14/983,746 filed on Dec.30, 2015, now U.S. Pat. No. 10,124,079, each of which is incorporated byreference herein in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to methods of administering [¹⁸F]-FACBC.The present disclosure also relates to use of [¹⁸F]-FACBC in methods forimaging, diagnosing and monitoring metastasis or recurrence of cancer.

BACKGROUND

Fluciclovine (¹⁸F) injection, also known as [¹⁸F]-FACBC, FACBC, oranti-1-amino-3-¹⁸F-fluorocyclobutane-1-carboxylic acid, is a syntheticamino acid imaging agent which is taken up specifically by amino acidtransporters and is used for positron emission tomography (PET). PET isuniquely suited to evaluate metabolic activity in human tissue fordiagnostic imaging purposes. [¹⁸F]-fluoro-2-deoxy-glucose (FDG) is a PETimaging agent for the detection and localisation of many forms ofcancer. However, FDG-PET has been found to have less sensitivity and/orspecificity for assessment of some types of cancer, for example,prostate cancer. [¹⁸F]-FACBC on the other hand shows great promise inthe imaging of a variety of cancers including primary and recurrentprostate cancer, as it has excellent in vitro uptake and low urinaryexcretion. PET imaging with [¹⁸F]-FACBC better defines tumours comparedto other known tracers such as FDG, allowing for better diagnosis andplanning of treatment, for example, by directing radiation therapy tothe appropriate areas.

Metastasis involves a complex series of steps in which cancer cellsleave the original tumour site and migrate to other parts of the bodyvia the bloodstream or the lymphatic system. The new occurrences oftumour thus generated are referred to as a metastatic tumour ormetastasis. Metastatic tumours are very common in the late stages ofcancer and are a major cause of death from solid tumours. Until now,[¹⁸F]-FACBC has not been reported as being used in the monitoring ofmetastatic cancer. There are known difficulties associated withdiagnosing and monitoring metastatic cancer, for example, obtaining twoor more images at different time points with enough accuracy to enablecomparison is challenging.

Thus there is a need for a method of imaging which allows forreproducible, reliable imaging for detection and monitoring ofmetastatic cancer.

SUMMARY

The present disclosure relates to methods of administering [¹⁸F]-FACBCfor improved PET imaging and more reliable diagnosis of metastasis orcancer reoccurrence. The disclosure further relates to a method ofdiagnosing metastasis or cancer reoccurrence using the PET imaging agent[¹⁸F]-FACBC.

In an aspect of the disclosure, there is provided a method ofadministering [¹⁸F]-FACBC to a subject comprising the steps of:

-   -   a) injecting a detectable amount of [¹⁸F]-FACBC into the right        arm of a subject, wherein said arm is positioned adjacent to the        subject's torso;    -   b) raising said arm in to an overhead position;    -   c) acquiring a PET scan image of the subject;        wherein said arm remains in the overhead position during the PET        scan.

In at least one embodiment, step c), i.e. image acquisition, startsabout 3 to 5 minutes after an injection of [¹⁸F]-FACBC has beenadministered, optionally 4 minutes after the end of the injection.

In a further aspect there is provided a method of imaging metastatic orrecurrent cancer in a subject, comprising the steps of:

-   -   a) administering to the subject a first dose of a detectable        amount of [¹⁸F]-FACBC and allowing time for the [¹⁸F]-FACBC to        accumulate at one or more areas of interest within the subject;    -   b) obtaining a first PET scan image of the subject;    -   c) administering to the subject a second dose of a detectable        amount of [¹⁸F]-FACBC and allowing time for [¹⁸F]-FACBC to        accumulate at one or more areas of interest within the subject;    -   d) obtaining a second PET scan image of the subject;        wherein the first and second scan images indicate the location        and intensity of [¹⁸F]-FACBC and wherein localisation of        [¹⁸F]-FACBC indicates the presence of tumour tissue in the        subject.

In one aspect there is provided a method of diagnosing or monitoringmetastatic or recurrent cancer in a subject, comprising the steps of:

-   -   a) administering to the subject a first dose of a detectable        amount of [¹⁸F]-FACBC and allowing time for the [¹⁸F]-FACBC to        accumulate at one or more areas of interest within the subject;    -   b) obtaining a first PET scan image of the subject, wherein the        scan image indicates the location and intensity of [¹⁸F]-FACBC;    -   c) administering to the subject a second dose of a detectable        amount of [¹⁸F]-FACBC and allowing time for [¹⁸F]-FACBC to        accumulate at one or more areas of interest within the subject;    -   d) obtaining a second PET scan image of the subject, wherein the        scan image indicates the location and intensity of [¹⁸F]-FACBC;    -   e) comparing the first and second scan images to determine        whether the location and/or intensity of [¹⁸F]-FACBC has        increased, remained constant, or decreased, thereby diagnosing        or monitoring metastatic or recurrent cancer in a subject.

In at least one embodiment of the second or third aspect, both PET andmagnetic resonance imaging (MRI) or x-ray computed tomography (CT) scanimages are acquired in steps b) and d), for example, by use of acombined PET-MRI or PET-CT system.

In an aspect of the disclosure there is provided a method of imagingmetastatic cancer in a subject, comprising i) administering [¹⁸F]-FACBCto a subject according to the first aspect; and ii) imaging the subjectaccording to the second aspect.

In another aspect, scanning is performed according to the followingparameters:

-   -   i) scanning starts 3 to 5 minutes after administration of        [¹⁸F]-FACBC, optionally about 4 minutes after administration of        [¹⁸F]-FACBC;    -   ii) scanning takes place in the direction of feet to head;    -   iii) for the first 2 or 3 bed positions, the scanning time per        bed position is of 4 to 5 minutes;    -   iv) for the subsequent bed positions, the scanning time per bed        position is of 2 to 3 minutes.

In at least one further embodiment, scanning starts at the proximalthigh. The scan may continue to the base of the skull.

In at least one further embodiment, scanning is completed within 30minutes of administration of [¹⁸F]-FACBC, which is the period duringwhich the signal to noise ratio is the highest.

Advantages and improvements associated with the administration protocoldescribed herein may include one or more of the following:

-   -   i) early imaging starting ˜4 min after injection    -   ii) starting at base of pelvis and working up,    -   iii) imaging for longer times/bed (4-5 mins) for the first 2-3        bed positions and then reverting to shorter times per bed (2-3        min).

What may be achieved clinically according to some embodiments of thepresent disclosure is sensitive detection of prostate cancer recurrencein practical imaging times. There are several factors at play which to acertain extent may compete with each other:

a) Disease spreads from the prostate/prostate bed generally upwards topelvic nodes, retroperitoneal nodes, pelvic bones or lumbar spine andthen to more superior (higher up) locations. Thus, it may make sense tolook ‘harder’ in these inferior (lower down) regions where diseasespread is more likely rather than higher up.b) Signal to noise for FACBC may be highest at time after injection of˜4 to 20-30 minsc) Imaging for longer times per bed can lead to better detection ofsmall lesionsd) It may be beneficial to get through at least 2 patients an hour perscanner in routine use.

Aspects of the present disclosure may balance one or more of thesefactors, e.g., in order to achieve a more time and cost efficientprocess.

In another aspect of the disclosure there is provided a method ofdiagnosing or monitoring metastatic cancer in a subject, comprising i)administering [¹⁸F]-FACBC to a subject using an administration protocolas described herein; and ii) diagnosing or monitoring metastatic cancer.

In a further aspect there is provided a kit for imaging, diagnosing ormonitoring metastatic cancer, comprising: a) [¹⁸F]-FACBC tracer; b)administration instructions according to the first aspect.

In an aspect of the disclosure there is provided the acquisition ofimages using a PET/MRI or PET/CT scanner. The simultaneous orconsecutive acquisition of images on a PET/MRI or PET/CT scanner may,for example, offer improved diagnostic accuracy over the generation ofimages on separate instruments. The conjoint use with MRI may improvethe localisation of tumours, particularly where the tumours are small,for example in the case of metastatic tumours. The method ofadministration can be embodiments of the method described herein.

DESCRIPTION OF THE DRAWINGS

FIGS. 1a and 1b show accumulation of FACBC in the Virchow's node whenthe FACBC is injected into the left arm. FIG. 1b shows stasis of tracer(circled). High ‘uptake’ of fluciclovine is demonstrated by the highstandardized uptake value (SUV) of >200 in the anatomical regionnormally associated with a Virchow-Troisier's Node.

FIG. 2 shows images from an example where FACBC accumulated in thebladder as the patient was over-hydrated. In this example, significanturine in the bladder, shown as a solid arrow, means that the prostatebed (inferior to the bladder) cannot be visualized.

FIG. 3 illustrates exemplary time activity curves showing rapid uptakeof fluciclovine (18F) in known prostate carcinoma recurrence, to amaximum at 4.5 minutes with a plateau to 30 minutes, which is followedby gradual clearance (9%/min) out to 60 minutes. Regions in marrow(ilium), muscle (gluteus), and bladder reached a plateau at 4.5 minutesthat remained constant throughout the imaging period.

FIG. 4 shows exemplary images before and after treatment for prostatecancer. Significant quantitative decrease in fluciclovine (18F) uptakepost therapy were seen showing that images taken at different timepoints can be compared (solid arrows).

DETAILED DESCRIPTION

The present inventors have established a protocol which may allow forthe reliable imaging of metastatic cancer, e.g., allowing the data fromPET scan images to be analysed and compared in order to accuratelydiagnose and/or monitor metastatic cancer.

The terms “approximately” and “about” refer to being nearly the same asa referenced number or value. As used herein, the terms “approximately”and “about” generally should be understood to encompass±5% of aspecified amount or value.

Disclosed is a method of detecting tumours in a patient comprisingadministering [¹⁸F]-FACBC to a subject and imaging the subject on aPET/MRI or PET/CT scanner to obtain conjoint PET and MRI images or PETand CT images. The tumours may be metastatic tumours. The administrationand/or PET imaging methods may be as described below.

In an aspect of the disclosure, there is provided a method ofadministering [¹⁸F]-FACBC to a subject comprising the steps of:

-   -   a) injecting a detectable amount of [¹⁸F]-FACBC into the right        arm of a subject, wherein said arm is positioned adjacent to the        subject's torso;    -   b) raising said arm in to an overhead position;    -   c) acquiring a PET scan image of the subject;        wherein said arm remains in the overhead position during the PET        scan.

In some embodiments, the right arm may be preferred as stasis in theaxillary vein upon injection in the left arm may be misinterpreted as ametastatic lymph node called Virchow's node, which is located in theleft supraclavicular fossa (the area above the left clavicle, or collarbone). For example, FIGS. 1a and 1b show accumulation of FACBC in theVirchow's node when the FACBC is injected into the left arm. FIG. 1bshows stasis of tracer (circled). In this example, high ‘uptake’ offluciclovine is demonstrated by the high standardized uptake value (SUV)of >200 in the anatomical region normally associated with aVirchow-Troisier's Node.

In step a), [¹⁸F]-FACBC is optionally injected over a time period ofabout 1 to 2 minutes, for example over about 1 minute. A relatively slowinjection bolus may be beneficial, e.g., because of a risk of a systemicreaction due to the relatively low pH dose striking the left ventricle.[¹⁸F]-FACBC may be injected by any suitable means in order for it toenter the bloodstream and/or the lymphatic system. Optionally, theinjection is an intravenous injection. The injection can be followed bya flush of about 10 mL or less.

In some embodiments, immediately after injection, for example less thanabout 10 seconds, less than about 5 seconds, or less about 2 secondsafter the end of the injection, the subject's arm is raised to anoverhead position prior to image acquisition. Optionally injection takesplace whilst the subject is lying down in a horizontal position withboth arms adjacent to the subject's torso, and immediately afterinjection both arms are raised into the overhead position prior to imageacquisition.

Amino acids are important nutrients for tumour growth. After injection,tumour cells may uptake [¹⁸F]-FACBC and the cells which have taken upthe tracer can be subsequently visualised. Acquisition can start 3 to 5minutes after the end of the injection, optionally 4 minutes after theend of the injection. [¹⁸F]-FACBC may be taken up by tumour cellsrelatively quickly compared to other PET radiotracers with differentuptake mechanisms. For example, In FDG-PET imaging, acquisition usuallystarts at least 45 minutes after injection.

A “detectable amount” of [¹⁸F]-FACBC refers to a dosage of [¹⁸F]-FACBCwhich is taken up by tumour cells allowing those cells to be detected byPET imaging. Optionally the dosage of [¹⁸F]-FACBC is between 250 and 500MBq, for example between 290 and 450 MBq, for example 370±20% MBq. Thedosage may be diluted up to 10 mL.

Optionally the patient fasts for at least 4 hours, for example 4 to 6hours, prior to administration of [¹⁸F]-FACBC. The term ‘fast’ means toconsume no food or drink. For example, only sips of water may beconsumed within the 4 hours prior to administration if needed for theadministration of medications. The consumption of water prior to[¹⁸F]-FACBC uptake may cause activity in urine in the bladder which maychallenge readings of images of the pelvic region. FIG. 2 showsexemplary images where FACBC has accumulated in the bladder as thepatient is over-hydrated. In this example, significant urine in thebladder, shown as a solid arrow, means that the prostate bed (inferiorto the bladder) cannot be visualized.

Optionally the patient avoids exercise a day before the scan through tothe time of the scan. Exercising may increase the demand by muscletissue for amino acids, which may result in general muscle uptake of the[¹⁸F]-FACBC tracer and can lead to unreliable readings.

The PET imaging technique utilises scanning devices that detect the 511keV annihilation photons that are emitted after radioactive decay offluorine-18. PET scanners are generally available for imaging of humansubjects. In addition, “micro-PET”scanners that have high spatialresolution can be used for imaging of small animals. In addition to PETscanners, ¹⁸F-radioactivity can also be monitored using one or moreradiation detector probes.

In another aspect there is provided a method of imaging metastaticcancer in a subject, comprising the steps of:

-   -   a) administering to the subject a first dose of a detectable        amount of [¹⁸F]-FACBC and allowing time for the [¹⁸F]-FACBC to        accumulate at one or more areas of interest within the subject;    -   b) obtaining a first PET scan image of the subject;    -   c) administering to the subject a second dose of a detectable        amount of [¹⁸F]-FACBC and allowing time for [¹⁸F]-FACBC to        accumulate at one or more areas of interest within the subject;    -   d) obtaining a second PET scan image of the subject;        wherein the first and second scan images indicate the location        and intensity of [¹⁸F]-FACBC and wherein localisation of        [¹⁸F]-FACBC indicates the presence of tumour tissue in the        subject.

In a further aspect there is provided a method of diagnosing ormonitoring metastatic cancer in a subject, comprising the steps of:

-   -   a) administering to the subject a first dose of a detectable        amount of [¹⁸F]-FACBC and allowing time for the [¹⁸F]-FACBC to        accumulate at one or more areas of interest within the subject;    -   b) obtaining a first PET scan image of the subject, wherein the        scan image indicates the location and intensity of [¹⁸F]-FACBC;    -   c) administering to the subject a second dose of a detectable        amount of [¹⁸F]-FACBC and allowing time for [¹⁸F]-FACBC to        accumulate at one or more areas of interest within the subject;    -   d) obtaining a second PET scan image of the subject, wherein the        scan image indicates the location and intensity of [¹⁸F]-FACBC;    -   e) comparing the first and second scan images to determine        whether the location and/or intensity of [¹⁸F]-FACBC has        increased, remained constant, or decreased.        In one embodiment of the second or third aspect, both PET and        magnetic resonance imaging (MRI) or x-ray computed tomography        (CT) scan images are acquired in steps b) and d), for example,        by use of a combined PET-MRI or PET-CT system.

In at least one embodiment, [¹⁸F]-FACBC is administered according to thefirst aspect of the present disclosure.

The time required for [¹⁸F]-FACBC to accumulate in tumour cells in stepsa) and c) of the aspects described above may be about 5 minutes or lessafter [¹⁸F]-FACBC is administered. Optionally, the time taken for[¹⁸F]-FACBC to accumulate is 3 to 5 minutes, for example 4 minutes. Thistherefore allows image acquisition to start 3 to 5 minutes afteradministration, for example 4 minutes after [¹⁸F]-FACBC administration.

FIG. 3 illustrates exemplary time activity curves showing rapid uptakeof fluciclovine (¹⁸F) in known prostate carcinoma recurrence, to amaximum at 4.5 minutes with a plateau to 30 minutes, which is followedby gradual clearance (9%/min) out to 60 minutes. Regions in marrow(ilium), muscle (gluteus), and bladder reached a plateau at 4.5 minutesthat remained constant throughout the imaging period.

During the PET scan the patient is optionally in the supine position andscanning takes place in the direction of feet to head. The start and endpositions of the scan may vary depending on the region of interest.Starting the scan at the proximal thigh and scanning to the base of theskull may capture the majority of lesions.

Once data has been collected from the first PET scan, the images can bevisualised and used to view the volume, shape and/or location of tumourcells within the subject. Images may be visually interpreted by anuclear medicine physician or radiologist and standardised uptake values(SUVs) such as SUVmax and SUVmean may be determined.

In at least another aspect, scanning is performed according to thefollowing parameters:

-   -   i) scanning starts 3 to 5 minutes after administration of        [¹⁸F]-FACBC, optionally about 4 minutes after administration of        [¹⁸F]-FACBC;    -   ii) scanning takes place in the direction of feet to head;    -   iii) for the first 2 or 3 bed positions, the scanning time per        bed position is of 4 to 5 minutes;    -   iv) for the subsequent bed positions, the scanning time per bed        position is of 2 to 3 minutes.

In at least one embodiment, scanning starts at the proximal thigh to thebase of the skull.

In at least one embodiment, scanning is performed between 3 to 30minutes after administration of [¹⁸F]-FACBC, which may be the periodduring which the signal to noise ratio is the highest.

The time between acquisition of the first and second PET scan images,i.e. between steps b) and d) of the aspects described above may be asmuch as one year. In some instances, the time between the first andsecond PET scans may be about 6 months, 5 months, 4 months, 3 months, 2months, 1 month or even less than about 1 month. It will be appreciatedthat steps c) and d) of the second and third aspects described above maybe repeated as many times as desired and/or necessary in order to obtainmultiple scan images which can be used to map the development of atumour over time.

Once image data has been collected from the second PET scan, the firstand second images may be visualised together and used to view the changein extent and location of tumour cells within the subject, allowing forthe diagnosis or monitoring of metastatic or recurrent cancer. Forexample, if the location of the tumour cells has changed then thesubject may be diagnosed with metastatic cancer. In some embodiments,the second scan image can be compared to images of data collected froman earlier PET scan taken before the first PET scan, in addition tocomparison with the first PET scan. In addition, any subsequent PET scanimages obtained after the second PET scan image can be compared with thefirst and/or second PET scan images.

By comparing the images from two or more differing time points, thedifferences in the tumour uptake of [¹⁸F]-FACBC can be analysed.Comparisons can involve qualitative image comparison (e.g., contrast oftumour uptake from background) and/or quantitative indices derived fromthe imaging or external radiation detection data (e.g., SUVs). Thedevelopment, progression or reduction of any tumours can therefore bemonitored and diagnosed accordingly. Suitable treatment can then bedetermined, for example, targeted administration of localised treatmentat the site of the tumour. It will be appreciated that the methodsdescribed herein can also be used to monitor response to varioustherapeutic regimens, including chemotherapy. FIG. 4 shows exemplaryimages before and after treatment for prostate cancer. Significantquantitative decrease in fluciclovine (¹⁸F) uptake post therapy wereseen showing that images taken at different time points can be compared(solid arrows).

The PET scan image obtained in steps b) and d) of the methods describedabove may be combined with, preceded or followed by anatomical imagingselected from computed tomography (CT) imaging, computerized axialtomography (CAT) imaging, MRI imaging ultrasound, or a combinationthereof. For combined imaging, the images can be acquired using adedicated PET-CT, PET-MRI, PET-ultrasound scanning device or separatePET and CT/MRI/ultrasound scanning devices. If separate PET andCT/MRI/ultrasound imaging devices are used, image analysis techniquescan be employed to spatially register the PET images with the anatomicalimages.

In at least one embodiment, the image acquisition steps b) and d)involve obtaining a combined PET scan image and MRI scan image. ThePET-MRI images can be obtained using a dedicated PET-MRI scanningdevice. Such scanning devices are available from Siemens (Biograph mMR)and GE (SIGNA PET/MR). Since MRI does not use any ionizing radiation,its use generally may be favoured in preference to CT in some instances.An advantage of PET-MRI acquisition may be that the patient and medicalstaff only need to be present for a single scan resulting in a more timeand cost efficient process.

In at least another embodiment, the image acquisition steps b) and d)involve obtaining a combined PET scan image and CT scan image. ThePET-CT images can be obtained using a dedicated PET-CT scanning device.An advantage of PET-CT acquisition may be that the patient and medicalstaff only need to be present for a single scan resulting in a more timeand cost efficient process.

The methods described herein can be used for intra-organ mapping oftumour location, for example, the spatial distribution of prostatecarcinoma within the prostate gland can be determined for aiding inbiopsy of the prostate gland or planning of radiation therapy of theprostate gland either by external beam radiation or brachytherapy.Likewise, the method may be used for guiding the biopsy or surgicalresection of lymph nodes.

The methods described herein are intended to be suitable for detectingmetastasis formation derived from primary prostate tumours. [¹⁸F]-FACBCcan be used in the detection and localisation of a wide variety ofmetastatic cancers. [¹⁸F]-FACBC may be particularly useful for imagingpelvic tumours, and metastases thereof in the pelvic lymph nodes.

In at least one embodiment, the methods of the disclosure are used todiagnose metastatic prostate cancer.

The methods described herein may be suitable for detecting recurrence ofprostate cancer. [¹⁸F]-FACBC may be particularly useful for imagingpelvic tumours, including prostate tumours and recurrence thereof in thepelvic lymph nodes.

In at least one embodiment, the methods of the disclosure are used todiagnose recurrent prostate cancer.

The methods of the present disclosure may be used in humans and/or maybe used in non-human animals (for example, dogs and cats).

Another aspect of the disclosure provides a kit for imaging, diagnosingor monitoring metastatic cancer, comprising: a) [¹⁸F]-FACBC tracer; b)administration instructions in accordance with the first aspect.

The following examples are intended to illustrate aspects of the presentdisclosure without, however, being limiting in nature. It is understoodthat the present disclosure encompasses additional embodimentsconsistent with the foregoing description and following examples.

EXAMPLES

Investigators from 3 different patient imaging sites were asked toselect 8 fluciclovine scans/cases from their past studies. The siteswere asked to select cases that covered a range of findings from subtleto obvious. The sites also submitted completed patient histories andunblinded read data that detailed the location of fluciclovine-avidlesions, SUVmax, reference tissue used in evaluating the lesion,target-to-reference tissue ratio, and the confidence rating of thepositive finding. The overall impression of level of confidence ofdisease in the prostate bed and in extra-prostatic areas was rated asProbably Negative, Probably Positive, or Confirmed Positive (1—Negative,2—Unlikely, 3—Equivocal, 4—Probable, 5—Definite). If Confirmed Positivewas selected, the method(s) of confirmation, defined as Histopathology,Standard of Care Imaging, or Clinical Follow-up, were to be selected.

The image acquisition and interpretation parameters and scannerinformation were compiled and presented in table format. Differences inacquisition parameters existed in the use of contrast, superior extentof the scan, minutes per bed position, acquisition of delayed images andhydration requirements. A summary of the data is presented below inTable 1:

TABLE 1 Image Acquisition Siemens mCT Scanner(s) GE Discovery STE GEDiscovery DLS GE 690 Biograph 40 GE 690 Acquisition 3D 2D 3D 3D 3D modeAttenuated CT 80 mA, 120 kVp, 16 75-160 mA, 120 kVp 75-160 mA, 120 kVp50 mA, 120 kVp 300 mA, 120 kVp Administered 370 MBq 370 MBq 370 MBq200*-400 MBq 3.5 MBq/kg activity *suboptimal Contrast No Yes, oral Yes,oral No Yes used? Position: Supine Supine Supine Supine SupineDirection: Feet first Head first Head first Head first Feet first ArmPosition Behind head Behind head Behind head Behind head Behind headStart Scan Mid-femur Symphysis pubis Below Proximal thigh Pelvis,centered Symphysis pubis over prostate End Scan Top of skull Abovediaphragm Above diaphragm Vertex Neck Minutes per 2 4 3 2 2.5 mindynamic bed pos. scan for 15 min Number of 8-9 3 4 7 +/− 1 5-6 bed pos.Uptake 3 min 5 min (end at 16) 5 min (end at 16) 5 min 0 min timeinitial Uptake N/A 17 min (end at 28) 17 min (end at 28) N/A N/A timesecond Uptake N/A 29 min (end at 40) 29 min (end at 40) N/A N/A timethird

It was noted that the patients who had activity in urine in the bladderwere more difficult to interpret with urinary excretion potentiallybeing confused with malignancy or smooth muscle uptake in urethra andunspecific uptake in the central zone. Dynamic uptake may possibly beuseful to differentiate between unspecific urethral/central zone uptakeand early urinary excretion. It had been the practice at some sites forpatients to drink water prior to the injection of fluciclovine. Theother sites did not prescribe hydration and had no issues with urine inthe bladder. It was concluded that patients should fast for at least 4hours prior to the scan, drinking only sips of water within 4 hoursprior to the scan, if needed for administration of medications. Somepatients demonstrated general muscle uptake of the tracer. In a numberof patients, some muscles showed particularly high uptake, believed tobe related to increased muscular activity, e.g., due to strenuousexercise. To avoid an increased demand by muscle tissue for amino acid,patients should not exercise from the day before the scan through to thetime of the scan.

All sites injected the tracer with arms down, and immediately after theinjection the arms were raised above the head to prepare for imaging. Insome patients stasis of the tracer in the axillary vein was noted. Thegroup concluded that the dosage of fluciclovine (370±20% MBq) shouldideally be diluted up to 10 mL and injected into the right arm, whenpossible, with the arms down and a slow push over 1 minute followed by≥10 mL flush.

The right arm is preferred as stasis in axillary vein may bemisinterpreted as a metastatic lymph node (Virchow's node). The armsshould be moved back to the scanning overhead position following thedosage and flush. Imaging should begin at 3 to 5 minutes with a goal of4 minutes from the end of the injection.

All sites scanned patients in the supine position in the direction offeet to head; however, the start and end positions of the scan itselfvaried. The group agreed that starting the scan at the proximal thighand scanning to the base of the skull would capture the vast majority ofthe lesions. Investigator A's scanning protocol was to scan to the domeof the diaphragm, then repeat a delayed scan starting again at thesymphysis pubis at approximately minute 17. The group reviewed imagesfrom both time points and agreed that the initial scan provided the mostuseful data. Investigator D performed dynamic scanning for 15 minutesover the pelvis before finishing with static scans to the neck. TheInvestigator D images were rebinned into 3×5 minute blocks, thus 0-5,5-10, and 10-15 minutes. The group reviewed all three time points. Theyagreed that the most useful images were in the 5-10 minutes window.While providing some interesting data points, data from the delayed anddynamic imaging sequences did not alter the result of the reads. Thisobservation further supported the proposed standardized acquisitionparameters. Thus it was concluded that for general clinical practice,patients should be imaged for a minimum of 3 minutes per bed position,extending to up to 5 minutes per bed position for the first two bedpositions, in a single, static scan. Imaging should begin at 4 minutesafter end of injection. For the CT parameters, a high-quality CT with nocontrast for clinical studies, and a 3 mm maximum slice thickness shouldbe employed. Contrast may be indicated in clinical trials.

Because of the known challenges with detection of small lesions in thesepatients, in general, the highest quality scanner at a site should beutilized. If a scanner has time-of-flight (TOF), iterativereconstruction and a reconstruction algorithm using recovery resolution,the features should be used. For quantitative assessment, the sitesshould reconstruct images using standardised reconstruction parametersspecific to the scanner being utilised.

In interpreting the images, all sites agreed on measuring lymph nodesize on CT and SUVmean and SUVmax on PET. The background referencetissue varied by site between blood pool, surrounding tissue, and marrowof the L3 vertebrae. Following the collaborative read of all images, aread consensus was developed that details the background tissuereference to be used. The tissue reference is dependent on the type(i.e., prostate bed, lymph node), size, and location of the lesion.

Consensus Group Image Read and Interpretation

The cases reads were determined to be concordant or discordant. To beconcordant, the blinded read had to match the unblinded read in allthree areas (bed, lymph nodes, distant disease such as bone) in overallpositive or negative for disease and, if positive, have disease noted inthe same specific area (e.g., left para-aortic lymph node, right iliacbone, etc.).

Investigators used a 5-point scale to assess their confidence in thepresence of positive findings. The scale was 1—Negative, 2—Unlikely,3—Equivocal, 4—Probable, 5—Definite. A rating of 1 or 2 would beconsidered Probably Negative, a rating of 4 or 5 would be consideredProbably Positive, and 3 would be equivocal. For the consensus groupread, the 6 experienced readers plus the independent reader sat at oneworkstation to review the cases together (utilizing the Volume Viewerapplication on the GE Advantage workstation). The investigators rotatedtime at the controls of the reading station, narrating how theyperformed image review. They noted how they approached the images,including use of the maximum intensity projection (MIP), windowing,change of windowing during the reading, planes of view, use of colourtables, and comparison with background reference tissue. The preferredapproaches of each were recorded and discussed after the first day ofreading. Prior to reading cases on day 2, the group defined the approachthey would use to review the cases. To start the review, readers usedwindowing procedures similar to (¹⁸F) FDG methods. Initially, the PETwindow is set so the liver and pancreas are intense. The optimum windowvaries for different tissue types. Suggested windows are 0 to 10 SUV forbone marrow, 0 to 7 SUV for lymph nodes, and 0 to 15 SUV for liver (theprecise appropriate windowing is scanner/workstation dependent).Multiple orthogonal planes (axial, saggital, and coronal) of view shouldbe used. It was also noted that the MIP is useful for detecting lesions,especially in bone but also lymph nodes. Colour tables are a personalpreference often based on the reading station and past experience.

The group reviewed the discordant cases that were identified from thepaired reads. The review included an oral summary of the relevantpatient history presented by clinical trial group staff as recorded onthe CRFs. The team then scrolled through the images, with oneinvestigator leading the image evaluation on the workstation. As eachcase was reviewed, the suspicious findings were compared to thosereported by the unblinded and blinded readers. In all cases, the blindedreader was in agreement with the unblinded reader at the conclusion ofthe review. Indeed, all investigators were in agreement on all findingson all patients with one exception (an indeterminant recurrence in theprostate bed versus physiologic uptake in smooth muscle).

At the conclusion of the discordant case review, the readers requested agroup review of all remaining cases, using the same reading format.These reads further refined the read methodology and the consensussummarisation of findings. Table 2 provides a summary of this review.

TABLE 2 Review of Discordant Cases Area of Unblinded Blinded DiscordantFindings Confidence Confidence Prostate bed 5 1 L3 Superior endplate 5 2(Schmorl's node) Unblinded investigator initially thought L3 Superiorendplate was a Schmorl's node. Confirmed metastasis with standard ofcare imaging and clinical follow-up. Prostate base 2 Left 5, Right 4 4(independent) Unblinded investigator called ‘probably negative;’however, blinded and independent reader read as probably and definitelypositive. The unblinded investigator changed the assessment to probablypositive (left 4, right 3) after the group review. Lymph nodes findings(4 nodes) were concordant across all readers. Internal iliac right lymphnode 4 3 The node was confirmed positive with standard of care imagingand clinical follow-up. The blinded reader changed the confidence to 4following group review. The bone lesion in the skull had been reviewedpreviously be the blinded reader so was not discussed. Retrocaval lymphnode 4 1. Not noted 2. Not noted Liver 2-3 1. Benign cyst 2. 4 Aftergroup review, both blinded readers called the retrocaval lymph nodepositive. A common iliac node was concordant. Ultrasound of the livershowed simple cysts. Blinded reader 1 cor- rectly identified the lesionas a benign cyst. Blinded reader2 changed the assessment to benign cyst.Right high obturator node 3 5 Following the group review, both theunblinded and blinded readers changed the confidence to 4. Positivefindings in the prostate bed were concordant. Of note, the patientreceived a dose of 250 MBq (wt. = 94 kg), producing a sub-optimal image.Prostate bed Not noted 4 Unblinded investigator assessed the prostatebed as ‘probably negative.’ The two blinded readers who were seeing theimages for the first time gave a confidence of equivocal. There was nopatient follow-up to confirm result. L3 vertebrae 2 5 L5 vertebrae 2 5Unblinded investigator read L3 as a Schmorl's node and L5 asdegenerative changes. Blinded reader assigned a confidence interval of 5to both vertebrae. Following the group review, the unblindedinvestigator increased to 3, the blinded reader decreased to 4, andinvestigators from the two other sites assessed a 3 and a 4, during theconsensus discussion. Two lymph nodes were read as concordant. Right10^(th) rib 5 4 4 Not noted Prostate bed* (not discordant) 3-4 1 1 1This case had 3 blinded readers; one did not note the rib lesion. Itshould be noted that the unblinded investigator initially missed thislesion, but it was found on a retrospective review. The unblindedinvestigator initially called the prostate bed as equivocal to probable.This was a false positive as confirmed by biopsy. All blinded readersinterpreted the images correctly.

SUMMARY

Over the course of the meeting, the group collectively reviewed 32 FACBCPET/CT image data sets. Fourteen patients were primary prostate cancerpatients and had not had a prostatectomy; 18 patients were statuspost-prostatectomy. There were 23 paired blinded and unblinded writtenimage read assessments. These formed the basis for the determination ofthe 8 discordant findings and 15 concordant patients. It should be notedthat cases with a discordant finding had other findings that wereconcordant. The ability of the investigators to correctly read theimages with no clinical history was well-documented.

Discordant cases were an important part of the learning experience forthe discussants, since it resulted in changes in their interpretationcriteria. Two sites shifted their sensitivity for reporting focalabnormal uptake, bringing them in line with the remainder of the group.

A summary of the standardized patient preparation and image acquisitionand reconstruction parameters are presented in Table 3.

TABLE 3 Image Acquisition, Reconstruction, and Interpretation GuidelinesScanner(s) Use highest quality scanner available Patient Fast >4 hrs,nothing by mouth except sips of water preparation for medications Nosignificant exercise from day before scan through to scan Acquisition 3D(if available) mode CT High-quality CT, no contrast in clinical study, 3mm slice thickness maximum Administered 370 MBq +/− 20% (dosage belowthat range result dose in low-quality images). Administer dose with armsdown, into right arm if possible. Dilute dosage up to 10 ml, slow pushover 1 minute, ≥10 ml flush. Move arms back to scanning positionfollowing dose and flush. Position: Supine Arm Position Behind headStart Scan Proximal thigh End Scan Base of skull Minutes per 3 min perbed position with up to 5 minutes for bed pos. first two bed positions(single static scan) Number of 4-5 as needed (depends on scanner fieldof view) bed pos. Uptake time 3-5 minutes with a goal of 4 minutes fromthe end initial of injection Recon- Use Point-Response-Functionreconstruction struction (resolution recovery or modulating) ifavailable for visual assessment. For quantitative assessment, imagesshould be reconstructed with 2 to 3 iterations, 20 to 28 subsets, andGaussian post reconstruction filter with 3-6 mm (dependent on scanner)

It is believed that utilization of these standardized interpretationcriteria may help to improve disease management, streamline patient careand reduce unnecessary treatments and medical costs.

Read Consensus for Recurrent Prostate Cancer

Following the consensus group read of the 32 image sets, the groupsummarized the read interpretation criteria for recurrent prostatecancer. The criteria use a comparison to background tissue to assign arelative uptake level. Uptake is defined as mild if the SUV of the areaof interest is greater than the SUV of the blood pool in the descendingaorta. Moderate uptake is defined as an SUV greater than bone marrow,typically in the lumbar vertebrae 3. Intense uptake is defined as an SUVvalue greater than that of the liver.

Prostate:

In general, as with other PET radiotracers, the more intense andnonphysiologic the uptake, the greater the possibility of a truepositive.

In the prostate bed in a patient who has had a prostatectomy,non-physiological uptake which is visually equal to marrow is suspiciousfor disease. But if a focus is small (<1 cm) and thus subject to partialvolume effect and in a suspicious location, it may still call suspiciousif it is visually greater than blood pool.

In the prostate bed in a patient who has not had a prostatectomy,moderate focal, asymmetric uptake visually greater than marrow issuspicious for residual or recurrent cancer. But if a focus is small (<1cm or <0.7 cm when a resolution recovery reconstruction algorithm isused) it may still be called suspicious because the uptake will beunderestimated, due to partial volume effect, if visually greater thanblood pool. Underestimation is valid not only for quantification, butfor visual assessment, as well. If the uptake is diffuse, heterogeneousand significantly greater than blood pool, it would be consideredsuspicious for disease (visually apparent). If the uptake is diffuse andhomogenous, a threshold of significantly greater than marrow (visuallyapparent) would apply. Anecdotally, median lobe uptake (central baseinvaginating into bladder) has a higher Fluciclovine uptake thanperipheral and central zones.

Extra-Prostate:

Ratios indicative of malignancy for suspected disease in the lymph nodesare dependent upon the size and the location of the nodes. If thesuspicious site is in a lymph node chain that is typical for prostaticmetastases, an uptake visually greater than marrow at L3 is consideredsuspicious. [ROC analysis of nodes of all sizes maximizes sensitivityand specificity with a node (SUVmax) to marrow (SUVmean at L3) ratio of1.2 or greater]. But if a node is small (<1 cm or <0.7 cm when aresolution recovery reconstruction algorithm is used) and subject topartial volume effect and in a suspicious location, it may still becalled suspicious if it is visually equal to marrow or significantlygreater than blood pool (recommend 1.5-2×).

For inguinal, distal external iliac, and axillary nodes, mild, symmetricslightly increased uptake is considered physiologic uptake. But if thenode is present within the context of other clear disease, it may alsobe considered suspicious. The presence of nearby vascular grafts ororthopaedic hardware could cause false positive uptake in these nodalgroups. In addition, distal external iliac nodes may also be suspiciousin isolation if above causes of false positivity are excluded includingrecent procedures and if the activity is greater than marrow.

For disease sites in bone, there may occasionally be an inverserelationship between fluciclovine uptake and the disease seen on CT.Focal bone lesion seen on MIP or PET only, is suspicious for disease.Sclerotic lesions showing cortical bone structure typical for benignosteomas on CT, without fluciclovine uptake are regarded as benign. Inpatients receiving antiandrogene therapy or after focal radiationtherapy of local bone metastases a bone lesion seen on CT seen as densesclerosis, with no focal uptake of fluciclovine on PET, is regarded asequivocal.

Sclerotic lesions with slightly, moderate or dense sclerosis orosteolysis on CT and focal elevated fluciclovine uptake are suspiciousfor disease. Bone metastases which resemble Schmorl's nodes, but withfluciclovine uptake within them, have been described. Correlation withCT scan, especially diagnostic, can be helpful in these cases.

Distribution of yellow and red bone marrow and can lead to focal areaswith slightly increased fluciclovine uptake in normal bone and make theappearance heterogeneous. If bone metastases are suspected, butfluciclovine results are negative, further evaluation with skeletalexaminations such as MRI, NaF PET/CT or bone scan with SPECT/CT may beneeded as fluciclovine alone may not be able to exclude metastases with100% confidence.

Although the present disclosure has been described above with referenceto specific embodiments, it is not intended to be limited to thespecific form set forth herein. Rather, the invention is limited only bythe accompanying claims and, other embodiments than the specificsdescribed above are equally possible within the scope of these appendedclaims.

The invention claimed is:
 1. A method of usinganti-1-amino-3-¹⁸F-fluorocyclobutane-1-carboxylic acid ([¹⁸F]-FACBC),comprising: a) administering the [¹⁸F]-FACBC in a dose of 370 MBq as anintravenous bolus injection into a human subject having a suspectedprostate cancer recurrence, wherein the [¹⁸F]-FACBC injection isfollowed by an intravenous flush; and b) acquiring a positron emissiontomography (PET) scan image of the human subject during a PET scan;wherein the human subject has: i. consumed no food or drink includingwater for at least 4 hours prior to the injection, except sips of waterfor taking medications, and ii. avoided significant exercise for atleast one day prior to the PET scan; wherein the human subject ispositioned in a supine position with arms above the head before the PETscan starts; wherein the PET scan starts 3 to 5 minutes after the end ofthe [¹⁸F]-FACBC injection; and wherein the PET scan starts from at leastthe human subject's proximal thigh and proceeds to the base of the humansubject's skull for a total scan time of up to 30 minutes.
 2. The methodof claim 1, further comprising analysing the PET scan image for a smalllesion less than 1 cm at a suspicious location, and identifying thelesion as suspicious for the prostate cancer recurrence if an uptake of[¹⁸F]-FACBC by the lesion is greater than blood pool.